1. Field of the Invention
The invention concerns a microbubble injector. In this context the term "microbubbles" designates bubbles of gas in a liquid with a diameter of between 50 and 100 micrometers approximately. They may be bubbles of air in water, for example.
2. Description of the Prior Art
The function of bubbles of this kind may be to facilitate the separation of solid and liquid phases. Microbubbles formed in a first liquid mass may, for example, be injected into a second liquid mass. This provides for the elimination of solid particles from this second liquid mass by flotation, that is to say by the attachment of bubbles to these particles so as to cause the latter to rise to the surface of the liquid from which they may be eliminated by mechanical means, for example.
More generally, the injection of microbubbles into a liquid can make it possible to modify its physical and chemical properties.
The best known method for producing microbubbles is to procure electrolysis between two electrodes in the liquid, the microbubbles being formed by a gas released by the electrolysis and appearing on one of the electrodes. This process is costly when a large number of microbubbles is to produced.
It has also been proposed to construct a microbubble injector which comprises a source of liquid under pressure. The liquid is able to vaporize at ambient temperature and contains a dissolved gas. An "injector" wall formed with an "injector" hole is used to procure a flow of this liquid at high velocity into a chamber containing a second liquid mass. There is thus obtained in the flow firstly a drop in the pressure of the liquid accompanied by the formation of vapor mixed with said gas and then an increase in pressure downflow because of deceleration of the flow with sudden condensation of the vapor and formation of microbubbles of the gas.
In this known injector the liquid flow in question naturally assumes the form of a rectilinear jet extending from the injector hole, and its deceleration results from it being slowed down in the liquid mass into which it is injected.
This known injector offers acceptable energy efficiency only when the jet is fine, this efficiency being defined as the ratio of the number of bubbles formed to the energy consumed in creating the jet. More precisely, the injector hole must be of small diameter, preferably less than 0.5 millimeters. As a result of this the number of injector holes must be large if the number of bubbles to be formed is large, which increases the overall dimensions of the injector. Moreover, there is a significant risk of these small holes being blocked by solid impurities, entailing interruptions in operation, unless highly efficient and therefore necessarily expensive filters are used.
The objective of the present invention is to produce a microbubble injector which is simple to manufacture, compact, highly energy efficient, reliable and easy to maintain, and which provides a high flowrate of microbubbles with only slightly differing diameters.